1987 Alpha One Gen One Upper drive shaft bearing preload

[roscottjr]

Could someone clarify how the upper drive shaft bearing preload is set. I have read the manual several times and best I can tell is the nut is tightened to 6-10 lb. in. while rotating the gears to be sure everything is seated correctly. This would explain why to use the correct loctite on these threads. Is this correct? I am resealing my upper unit due to a leaking seal and have acquired the necessary tools, I just need to clarify this bearing preload. Or is this simply the amount of effort required to turn the shaft in the bearing assembly?

 

[ziggy]

Re: 1987 Alpha One Gen One Upper drive shaft bearing preload

Or is this simply the amount of effort required to turn the shaft in the bearing assembly?

that's the way i understand it.
i just checked mine for having the driven gear shaft upper brg. replaced. i used the same amount of shim stack that the old brg. had. after replacing the brg and race i put the cap back on and torqued it's 4 bolts to spec. (20 ft. lbs on my pre alpha), then used a lower drive shaft to turn the assy. (the driven gear shaft installed by it self) your spec of 6-10 in. lbs. rolling torque sounds about right, think i came in at 5 or 6. i was working on my pre alpha. so i suppose what i'm saying might not apply to your alpha1. but w/o looking at a book. i'll speculate it is. the pros will correct me if i'm out of line.

fwiw. my local mercrusiser tech says the shim stack that's in place will be what it needs. he contends that the reason for needing shims is that the cases are all a little different. hence the need for shims. once shimmed proper. he says it'ls likely that will be the right shim stack even when replacing brgs. so far i've replaced the above mentioned brg. _ the double brg. stack on the drive gear shaft. both times i ended up with the same amount of shims as i started with. i'm starting to believe my local tech.

 

[Don S]

Re: 1987 Alpha One Gen One Upper drive shaft bearing preload

There is no nut to torque down, the only nut is the one on the end of a vertical driveshaft from the lower unit that you use to turn the gear. How many inch pounds (6-10) is the amount of force need to turn the shaft which is splined into the vertical shaft of the upper gear unit.
You should be looking at pages 3A-26 & 27 of the manual, step 11 explains it.

 

[roscottjr]

Re: 1987 Alpha One Gen One Upper drive shaft bearing preload

Thanks ziggy and Don. I just wanted to be sure what I was reading was correct. Now I just need to locate an appropriate torque wrench.

ziggy, I have rebuilt several lower units for outboards but this is my first sterndrive. On the others I rebuilt I was told the same thing as far as the shims go. I normally check all parts with calipers and micrometers to verify the measurements are the same and so far they have been unless replacing the case too.

Robert

 

[Don S]

Re: 1987 Alpha One Gen One Upper drive shaft bearing preload

Do you have the tools to check gear heights? If you change any shims, even for preload, you will change gear heights.

 

[roscottjr]

Re: 1987 Alpha One Gen One Upper drive shaft bearing preload

I dont own those tools but I do have access to them. The drive is going back as it was, just resealing the unit but I will be checking all tolerances just as if it were all new gears, bearings, and case just to be sure everything is within spec.

 

[6meter]

Re: 1987 Alpha One Gen One Upper drive shaft bearing preload

that's the way i understand it.
fwiw. my local mercrusiser tech says the shim stack that's in place will be what it needs. he contends that the reason for needing shims is that the cases are all a little different. hence the need for shims. once shimmed proper. he says it'ls likely that will be the right shim stack even when replacing brgs. so far i've replaced the above mentioned brg. _ the double brg. stack on the drive gear shaft. both times i ended up with the same amount of shims as i started with. i'm starting to believe my local tech.

Its no different in rear ends of rear wheel drive cars and pickups. When replacing the bearings, reuse the same shims. the castings are bored close but not exact. Bearings are made with ALOT more precision.

 

[Don S]

Re: 1987 Alpha One Gen One Upper drive shaft bearing preload

The drive is going back as it was, just resealing the unit

If you are re using the bearings, then you shouldn't be using the 6-10 in lb. spec, you should be using the 2.5-4 spec.

 

[roscottjr]

Re: 1987 Alpha One Gen One Upper drive shaft bearing preload

If you are re using the bearings, then you shouldn't be using the 6-10 in lb. spec, you should be using the 2.5-4 spec.

Absolutely. I only used the "new" specs because I had checked on new gears and bearings before I tore it all down and the specs for new parts was still on my mind. I am shooting for 3 in lb when I reassemble everything. The only issue right now is the torque wrench. The only one I have located is $200+ so I am looking for one a little cheaper. I dont want to go the cheap unreliable route but definately cheaper than $200. The person I borrowed the other tools from doesnt even have one. It may be loaned out to someone, good thing he is not very busy right now cause I have most of his Alpha outdrive tools. My father in law and I teamed up and made the bearing carrier puller that carries a $400 price tag. It is not very pretty but it did the job perfectly.

 

[roscottjr]

Re: 1987 Alpha One Gen One Upper drive shaft bearing preload

Another question, I have a long yoke from another outdrive, can this be used to check engine allignment?